This invention relates generally to the field of radiation detector devices, and more specifically to thick film, fast response detectors of infrared radiation, which are hardened against damage by laser radiation.
Thermal detectors having fast response times finding substantial prior use have included both thermocouple and bolometer types, wherein heat sensitive elements of the detectors, through changes in resistance, provide a measure of the intensity of the radiation to which the detector is exposed. Although the sensitivity of these detectors may be low compared to other types of radiation detectors, their use for the detection of high intensity radiation from lasers is desirable. The bolometer type detector is the more desirable configuration for use in detection of high energy laser radiation because the bolometer provides voltage signals greater than those obtained from the thermocouple detector, and thus requires a lesser degree of amplification of the signals. Further, the bolometer has a better defined area of radiation detection. Therefore, the bolometer may be more accurately calibrated than the thermocouple detector.
Prior art devices for the detection of infrared radiation, and particularly laser radiation have included various thin film or thick film configurations as are disclosed by or referenced in U.S. Pat. No. 3,898,605 disclosing a bolometer in the form of a thin film of Bi or Ni evaporated onto a high thermal conductivity infrared waveguide with electrical contacts applied to each end of the thin film; U.S. Pat. No. 4,117,329 disclosing a thin film photoconductive detector comprising a thin (one micron) film of PbS on substrates of quartz, strontium titanate and silicon; U.S. Pat. No. 4,001,586 disclosing an infrared intrusion detector employing a chip or flake of cobalt oxide as the thermosensitive material; U.S. Pat. No. 4,061,917 disclosing a bolometer utilizing a thin (100-1000 A) film of bismuth on a substrate of alumina coated aluminum.
Existing detectors of infrared radiation, and particularly laser radiation, often are destroyed or have their operating characteristics altered by the very radiation they detect. Further, such devices, being thermosensitive, do not adequately provide for the effect of ambient temperature fluctuations on output, which adversely affects their reliability.
The present invention provides a novel thick film laser radiation detector having fast frequency response and a high damage threshold, and comprises a thick film of thermistor material on a substrate having high thermal conductivity. The detector is uniquely configured to provide rapid heat dissipation, and thus room temperature detection of high intensity infrared radiation, such as laser radiation, can be performed without damage to the detector. The detector may be configured in a pair of film elements to compensate for ambient temperature fluctuations. Further, a plurality of pairs may be configured into an array to determine the intensity profile of a continuous laser beam.
It is therefore an object of this invention to provide an improved radiation detector.
It is a further object of this invention to provide an improved laser radiation detector having a high damage threshold.
It is a further object of this invention to provide a laser radiation detector in which the effect of ambient temperature fluctuations is minimized.
It is a still further object of this invention to provide a laser detector system for determining the profile characteristics of an impinging laser beam.
These and other objects of the present invention will become apparent as the detailed description of certain embodiments thereof proceeds.